Radiative capture and photodisintegration reactions for the synthesis of the p nuclei Philipp Scholz for the group of Prof. Dr. Andreas Zilges Institute for Nuclear Physics, University of Cologne Workshop on New Vistas in Low- Energy Precision Physics (LEPP) April 4 th -7 th , 2016 Supported by the ULDETIS project within the UoC Excellence Initiative institutional strategy and by DFG (ZI 510/8-1,INST 216/544-1). * Partly supported by the Bonn-Cologne Graduate School of Physics and Astronomy. Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
Outline Introduction Nucleosynthesis of heavy elements and the p nuclei the g -process reaction network Experimental measurements of cross-sections photo-inducedreaction measurements charged-particleinduced reaction studies Experimental results testing the E1-strength in 90 Zr via 89 Y(p, g ) total and partial cross sections for 92 Mo(p, g ) P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
The synthesis of the p nuclei T. Rauscher et al. , Rep. Prog. Phys. 76 (2013) 066201 p nuclei 30-35 neutron deficient isotopes cannot be produced by neutron- capture reactions relativelylow isotopic abundances M. Arnould et al. , Phys. Rep. 450 (2007) 97 in comparison to s - and r -isotopes originallythought to be produced via proton-capture temperatures would lead to immediate photodisintegration P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
The synthesis of the p nuclei g process reaction-network huge photodisintegration reaction-network at temperatures between 1.5 GK and 3 GK in ccSN or type Ia SN starting from stable seed nuclei formed in the s - or r -process g -process path proceeds first via ( g ,n) reactions branching for A < 130 mainly via ( g ,p) above A > 130 ( g , a ) get more important P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
The synthesis of the p nuclei reaction-network calculations g -process network calculations cannot reproduce solar system abundance other contributions from rp-, a - or other processes? problems with photoinduced reaction cross sections? S.E. Woosley and W. M. Howard, ApJSS 36 (1978) 285 P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
Experimental measurements of cross sections Photodisintegration separationenergy S n or S p n or p g g b A X A‘ Y measuring cross sections via direct detectionof ejectilesor via photoactivation using either monochromatic g -ray beams or Bremsstrahlung P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
Experimental measurements of cross sections Ground-state contributions measured cross sections cannot directly used for astrophysics for g -induced reaction the ground-state contribution is almost zero larger contribution from excited states in the stellar plasma (T 9 > 1.5) reaction rates are obtained from the inverse reactions via reciprocitytheorem ( g ,n) ( g ,p) ( g , a ) T . Rauscher, ApJSS 201 (2012) 26 P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
Experimental measurements of cross sections Statistical model cross sections in the Gamow window are small ( < µb) most of the reactions are not accessiblein the laboratory reaction rates are calculated mostly in the scope of the statistical model cross-section measurements to improve nuclear physics input- parameters: g -strength function (also via ( g,g ’)) particle + nucleus optical model potentials P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
Charged-particle induced reaction cross sections Activation technique widely used technique for measureing cross-sections temporal and spatial separation of irradiation and spectroscopy no access to reactions involving stable reaction products feasible half-lives neccessary P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
Charged-particle induced reaction cross sections Activation technique widely used technique for measureing cross-sections temporal and spatial separation of irradiation and spectroscopy no access to reactions involving stable reaction products feasible half-lives neccessary 4 p summing crystal method complete deexcitation is summed up in one peak access to stable reaction products need for very different Q-values for competing reactions no access to partial cross-sections P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
Charged-particle induced reaction cross sections Activation technique widely used technique for measureing cross-sections temporal and spatial separation of irradiation and spectroscopy no access to reactions involving stable reaction products feasible half-lives neccessary 4 p summing crystal method complete deexcitation is summed up in one peak access to stable reaction products need for very different Q-values for competing reactions no access to partial cross-sections In-beam method with HPGe detectors P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
In-beam technique with HPGe detectors de-excitation of the entry state E p determination of partial • cross sections very sensitive on the g -ray • strength function + Q P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
In-beam technique with HPGe detectors de-excitation of the entry state E p determination of partial • cross sections very sensitive on the g -ray • strength function + Q transitions to the ground state determination of the total • cross section P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
In-beam technique with HPGe detectors 10 MV FN-Tandem ion accelerator HORUS γ -ray spectrometer 14 HPGe detectors High resolution • ≈ 2 keV @ 1332 keV High total efficiency • ≈ 2% @ 1332 keV 5 different angles with respect to beam axis determination of angular • distributions BGO shields L. Netterdon et al. , NIM A 754 (2014) 94-100 P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
In-beam technique with HPGe detectors Target chamber cooling trap tantalum coating independent current readouts δ -electron suppression built-in detector for Rutherford Backscattering Spectrometry (RBS) L. Netterdon et al. , NIM A 754 (2014) 94-100 P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
In-beam measurement of the 89 Y(p, g ) reaction in a region which is normally underproduced in reaction network 93 Tc calculations total cross section was measured twice 92 Mo 94 Mo before 91 Nb 92 Nb 93 Nb g -ray strength function in 90 Zr was measured before 90 Zr 91 Zr 92 Zr natural yttrium target (583µg/cm²) 89 Y beam currents between 1nA and 60nA 86 Sr 87 Sr 88 Sr five different proton energies between 3.65 MeV and 4.70 MeV, i.e. g -ray energies between 7.71 MeV and 12.98 MeV (Q-Value: 8353.4 keV) P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
In-beam measurement of the 89 Y(p, g ) P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
In-beam measurement of the 89 Y(p, g ) P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
In-beam measurement of the 89 Y(p, g ) g 3 g 4 g 5 g 0 g 1 g 2 L. Netterdon et al. , PLB 744 (2015) 358 P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
In-beam measurement of the 89 Y(p, g ) 89 Y(p, g ) partial cross sections: huge deviations P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
In-beam measurement of the 89 Y(p, g ) using g - strength function from ( g,g ’ ) measurement: R. Schwengner et al. , PRC 78 (2008) 064314 P. Scholz, AG Zilges, IKP, Universität zu Köln Radiative capture and photodisintegration reactions P. Scholz, AG Zilges, University of Cologne
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